CHRONIC MYELOGENOUS AND ADULT LYMPHOBLASTIC LEUKEMIA
Leukemia is a malignant condition of white blood cells in which bone marrow is diffusely replaced by relatively immature white blood cells which generally also appear, in large numbers, in the circulating blood (Robbins and Angell, 1976, in "Basic Pathology", Second Edition, W. B. Saunders Co., Philadelphia, pp. 349-354). Leukemias may be classified as acute lymphocytic (or lymphoblastic), chronic lymphocytic, acute myelogenous, or chronic myelogenous.
Chronic myelogenous leukemia (CML) accounts for approximately 25 percent of all leukemias. Onset of the disease occurs most frequently in middle age, with males and females affected approximately equally. CML is generally associated with prominent enlargement of the spleen. Prognosis for survival is approximately three to four years.
The clinical progression of CML may be divided into two phases, a chronic phase and a blastic phase (Canellos (1983) in "Harrison's Principles of Internal Medicine", Petersdorf et al., eds., Tenth Edition, McGraw Hill Book Company, N.Y., pp. 808-810). During the chronic phase, there is a proliferation and accumulation of polymorphonuclear leukocytes and granulocytic (myeloid) cells of intermediate maturity; myeloblasts usually account for less than ten percent of cells in the bone marrow and peripheral blood. The chronic phase typically persists for a median of 36 to 40 months before the onset of the blastic phase. During the blastic phase, there is a dramatic increase in the number of undifferentiated cells. In about one third of CML blastic phase cases, the blast cell morphology has some of the characteristics of lymphoblasts, including expression of the enzyme terminal deoxynucleotidyl transferase and reactivity with a non-B, non-T anti-acute lymphoblastic leukemia antiserum.
Acute lymphocytic (or lymphoblastic) leukemia accounts for about 20 percent of all leukemias, occurs predominantly in children, and develops more frequently in males than in females. Untreated, the prognosis for survival is approximately four months; with treatment, survival may be for several years and some cures have been reported (Robbins and Angell, supra). The leukemic cells of about 75 percent of patients with ALL are often termed "null" cells because they lack B and T cell markers.